上海交通大学：《飞机设计 Aircraft Design》课程教学资源_参考资料_36_engine options for supersonic cruise aircraft AIAA-1978-1054-507

Sponsored by- American Institute of Aeronautics and Astronautics(AIAA) Society of Automotive Engineers(SAE) 78-1054 Engine Options for Supersonic Cruise Aircraft P.H.Calder and P.C.Gupta,Bristol Engine Division,Bristol,UK AIAA/SAE 14TH JOINT PROPULSION CONFERENCE Las Vegas,Nev./July 25-27,1978 For permission to copy or republish,contact the American Instltute of Aeronautics and Astronautics, 1290 Avenue of the Americas,New York,N.Y.10019

Sponsored by￾American Institute of Aeronautics and Astronautics (AIAA) Society of Automotive Engineers (SAE) 78-1054 Engine Options for Supersonic Cruise Aircraft c P. H. Calder and P. C. Gupta, Bristol Engine Division, Bristol, UK AIANSAE 14TH JOINT PROPULSION CONFERENCE Las Vegas, Nev.lJuly 25-27, 1978 For permission to copy or republish. contact the Amerlcan lnstltute of Aeronautics and Astronautics, 1290 Avenue of the Americas, New Vork. N.V. 10019

ENGINE OPTIONS FOR SUPERSONIC CRUISE AIRCRAFT Dr P H Calder,OBE Project Director Olympus 593 and P C Gupta Assistant Chief Engineer-Performance Rolls-Royce Limited,Aero Division,Bristol Abstract integrated with the development of the variable throat,variable divergence, The paper summarises the Supersonic thrust reversing exhaust system,which uses Cruise engine studies that have been intake throat bleed for ventilation. These carried out as part of the UK contribution have been four-company activities as has to the ICAO Noise Working Group activities, been the flight clearance of the powerplant and presents the results of their inte- to the stringent airworthiness criteria laid gration in the Aircraft Parametric Study by down jointly by the British and French British Aerospace.Duct burning and Authorities, variable cycle engines are also discussed. The recent Rolls-Royce experimental work on If the cowlings of one of the rectangu- co-annular nozzles and mechanical ejector lar paired nacelles are removed,two square suppressors is reviewed and an international engines are visiblel This is the result of collaborative programme on mechanical tailoring the mass of engine dressings, ejector suppressor testing is described. It is shown how the choice of engine cycle cables and pipework to the nacelles.See Figure1· depends on the characteristics of the air- craft,the amount of silencing available and the level of technology available at go-ahead. NOT TO BE USED. THIS FL.AP ERATW Introduction Concorde supersonic passenger services from Paris and London to South America and the Middle East commenced nearly two and a half years ago and were extended to North America two years ago,initially to Washington DC and then to New York. At the end of April 1978 some 54 000 hours of engine service experience had been accumulated in the course of 4500 flights. Concorde and its powerplant have met their payload range performance objectives. The aircraft had made convincing demonstra- tions,even before the commencement of ser- vice into New York,that it had met its design aim of being no noisier than narrow bodied aircraft (707,DC8,VC10).In fact under certain circumstances,and due to its Fig 1.Concorde Engine Bay ability to adapt to particular airport geography,Concorde can produce community The last of the batch of engines ordered noise levels which are appreciably lower for the first sixteen Concorde aircraft was than those of narrow bodied aircraft. passed off the test bed in December 1977. Early flight development engines continue The theme of this session is SST to be converted to production standard for Propulsion System Airframe Integration. spares. The Concorde is a flying example of such integration,From the very earliest design It is appropriate at this time to examine stages the integration of the engine and the performance of the production run of powerplant with the airframe has been a new engines.Figure 2 shows that the prime consideration,with all relevant guaranteed thrust and mission equivalent decisions being mutually agreed by the four specific.fuel consumption have been met Companies responsible,The development of with comfortable margins and that the mean the variable intake to match the engines, performance has achieved the brochure target and control of the engine to match the which was used for aircraft mission per- intake under certain flight conditions,was formance predictions. Copyrightmerican Institute of Aeronautics and stronautics,Inc.,1978.All rights reserved

ENGINE OPTIONS FOR SUPERSONIC CRUISE AIRCRAFT Dr P H Calder, OBE Project Director Olympus 593 and P C Gupta Assistant Chief Engineer - Performance Rolls-Royce Limited, Aero Division, Bristol Abstract The paper summarises the Supersonic Cruise engine studies that have been carried out as part of the UK contribution to the ICAO Noise Working Group activities, and presents the results of their inte￾gration in the Aircraft Parametric Study by British Aerospace. Duct burning and variable cycle engines are also discussed. The recent Rolls-Royce experimental work on co-annular nozzles and mechanical ejector suppressors is reviewed and an international collaborative programme on mechanical ejector suppressor testing is described. It is shown how the choice of engine cycle depends on the characteristics of the air￾craft, the amount of silencing available and the level of technology available at go-ahead. Introduction Concorde supersonic passenger services v from Paris and London to South America and the Middle East commenced nearly two and a half years ago and were extended to North America two years ago, initially to Washington Dc and then to New York. At the end of April 1978 some 54 000 hours of engine service experience had been accumulated in the course of 4500 flights. Concorde and its powerplant have met their payload range performance objectives. The aircraft had made convincing demonstra￾tions, even before the commencement of ser￾vice into New York, that it had met its design aim of being no noisier than narrow bodied aircraft (707, Dc8, VClO). In fact, under certain circumstances, and due to its ability to adapt to particular airport geography, Concorde can produce community noise levels which are appreciably lower than those of narrow bodied aircraft. The theme of this session is SST Propulsion System - Airframe Integration. The Concorde is a flying example of such integration. From the very earliest design stages the integration of the engine and powerplant with the airframe has been a prime consideration, with all relevant decisions being mutually agreed by the four Companies responsible. The development of the variable intake to match the engines, intake under certain flight conditions, was / and control of the engine to match the 1 Copyrl@lO American in~lilutc of AeroniUlks *ad Astronm~ica. In<.. 1978. All rights resewed. integrated with the development of the variable throat, variable divergence, thrust reversing exhaust .syrtAm-! -which uses intake throat bleed for ventilation. These have been four-company activities as has been the flight clearance of the powerplant to the stringent airworthiness criteria laid down jointly by the British and French Authorities. If the cowlings of one of the rectangu￾lar paired nacelles are removed, two square engines are visible! This is the result of tailoring the mass of engine dressings, cables and pipework to the nacelles. See Figure 1. Fig 1. Concorde Engine Bay The last of the batch of engines ordered for the first sixteen Concorde aircraft was passed off the test bed in December 1977. Early flight development engines continue to be converted to production standard for spares. It is appropriate at this time to examine the performance of the production run of new engines. Figure 2 shows that the guaranteed thrust and mission equivalent specific fuel consumption have been met with comfortable margins and that the mean performance has achieved the brochure target which was used for aircraft mission per￾formance predictions

》4CH2SA+5吃GR%EnRs7 MEAN-1032 号 A∽ L96 答9n7和m+院 N.26r 注6%》 BIO MIIMLIM ACCEPONCE OMARIMM ACEPTANE BROCHARE NOMINAL MN,--/3% 05 ENEINE SERAL N9 845se47 Fig 2. Olympus 593 Mk 610 Performance of Fig 3. Effect of Cycle on Payload at Fixed New Production Engines (Assessed at Range Nominal Control Schedule Settings) Only two of the engines were rejected on datum value,results in a loss in payload. the first acceptance run,due in both cases The turbojet had optimum performance,a to low TET,and hence thrust,at limiting conclusion that had been reached indepen- HP spool rpm or measured EGT. In both dently by Government establishments. cases a change in component enabled the Concorde was designed to have no higher engine to be cleared. noise levels than the subsonic narrow bodied jets (707,VC10 etc)which were expected to The successor to Concorde must not only form the major part of airport movements at be economically viable,but must be the envisaged entry-into-service date. The environmentally acceptable. In their 1977 results of monitoring of Concorde operations paper to the AIAA/SAE Propulsion Conference into Washington and New York have confirmed the authors reviewed the application of new that this target has been achieved. technology to meet these aims,and discussed the constraints involved with particular Considerations of optimisation of mission reference to pollution and noise. Prior to fuel,including the quite considerable sub- that date ICAO had addressed the matter of sonic element in the reserves,led to the noise regulations for present and future choice of overall pressure ratio adopted. supersonic transport aircraft,and Apart from the engine cycle,other engineer- initiated a number of studies which have ing considerations were of major importance. been proceeding over the last year. This The Olympus family of engines had a large paper gives the results of some of the UK background of experience,and a supersonic contributions to these studies which are version was already under development for relevant to the choice of engine for a a military tactical strike aircraft (TSR2) supersonic cruise aircraft,and goes on to which was later cancelled,but not before discuss further options such as duct the engines had flown, burning and cycle variability in the light of these studies.The paper also summarises Furthermore,the Bristol part of the recent and proposed experimental work on Rolls-Royce organisation (Bristol Siddeley silencing, covering the results of Engines Limited as it was then known) co-annular nozzle noise measurements, and already had collaborative arrangements with including some details of a proposed the French engine company SNECMA. international collaboration programme to advance the technology of ejector These considerations weighed heavily in suppressors. favour of the choice of an olympus derivative,once the choice of engine cycle had been made,During the design and Choice of Engine for Concorde development of the engine and powerplant the Figure 3,which is reproduced from maximum possible amount of variability was Reference 1,shows the relationship trends incorporated to obtain the best performance and lowest noise within the constraints of between payload,TET,bypass ratio and jet velocity. It takes into account both the available technology. specific fuel consumption and powerplant weight and drag effects using Concorde as Figure 3 also shows how,as technology a datum at fixed range. advances,the use of increased TET would permit the bypass ratio to be increased and jet velocity reduced without sacrifice in At the cruise turbine entry temperatures (ueowethatn payload,and that an improved payload is obtained with higher TET if the jet velocity addition of bypass,to reduce jet velocity is held constant,or allowed to rise. at take-off and flyover (cut-back)from the 2

Fig 2. Olympus 593 Mk 610 Performance of New Production Engines (Assessed at Nominal Control Schedule Settings) Only two of the engines were rejected on the first acceptance run, due in both cases to low TET, and hence thrust, at limiting HP spool rpm or measured EGT. In both cases a change in component enabled the engine to be cleared. ' The successor to Concorde must not only be economically viable, but must be environmentally acceptable. In their 1977 I paper to the AIAA/SAE Propulsion Conference the authors reviewed the application of new technology to meet these aims, and discussed the constraints involved with particular reference to pollution and noise. Prior to that date ICAO had addressed the matter of noise regulations for present and future supersonic transport aircraft, and initiated a number of studies which have been proceeding over the last year. This paper gives the results of some of the UK contributions to these studies which are relevant to the choice of engine for a supersonic cruise aircraft, and goes on to discuss further options such as duct burning and cycle variability in the light of these studies. The paper also summarises recent and proposed experimental work on silencing, covering the results of co-annular nozzle noise measurements, and including some details of a proposed international collaboration programme to advance the technology of ejector suppressors. Choice of Encline for Concorde Figure 3, which is reproduced from Reference 1, shows the relationship trends between payload, TET, bypass ratio and jet velocity. It takes into account both specific fuel consumption and powerplant weight and drag effects using Concorde as a datum at fixed range. At the cruise turbine entry temperatures envisaged at Cgncorde's early design stage (135OOK - 1400 K) Figure 3 shows that any addition of bypass, to reduce jet velocity at take-off and flyover (cut-back) from the 2 Fig 3. Effect of Cycle on Payload at Fixed Range datum value, results in a loss in payload. The turbojet had optimum performance, a conclusion that had been reached indepen￾dently by Government establishments. Concorde was designed to have no higher noise levels than the subsonic narrow bodied jets (707, VClO etc) which were expected to form the major part of airport movements at the envisaged entry-into-service date. The results of monitoring of Concorde operations into Washington and New York have confirmed that this target has been achieved. Considerations of optimisation of mission fuel, including the quite considerable sub￾sonic element in the reserves, led to the choice of overall pressure ratio adopted. Apart from the engine cycle, other engineer￾ing considerations were of major importance, The Olympus family of engines had a large background of experience, and a supersonic version was already under development for a military tactical strike aircraft (TSRZ) which was later cancelled, but not before the engines had flown. Furthermore, the Bristol part of the Rolls-Royce organisation (Bristol Siddeley Engines Limited as it was then known) already had collqborative arrangements with the French engine company SNECMA. These considerations weighed heavily in favour of the choice of an Olympus derivative, once the choice of engine cycle had been made. During the design and development of the engine and powerplant the maximum possible amount of variability was incorporated to obtain the best performance and lowest noise within the constraints of the available technology. Figure 3 also shows how, as technology advances, the use of increased TET would permit the bypass ratio to be increased and jet velocity reduced without sacrifice in payload, and that an improved payload is obtained with higher TET if the jet velocity is held constant, or allowed to rise

Advancements in Technology The United Kingdom study is being under- taken by British Aerospace (Filton and In Reference 1 the authors have reviewed Weybridge)with engine data supplied by the application of advancements in tech Rolls-Royce.In this study British nology to the performance improvement and Aerospace are evaluating operating costs noise reduction of supersonic transport and noise levels of a family of aircraft. aircraft.It is shown how performance The study covers variations in: requirements for subsonic aircraft have led to the adoption of low specific thrust, Range high bypass ratio engines,with a consequent Number of Passengers reduction in jet velocities and hence in Wing Area airport noise.It is also shown that this Aspect Ratio is not the case for supersonic cruise air- Engine Bypass Ratio craft where increasing bypass ratio beyond a certain value will degrade the mission Class II technology is being assumed,with performance (Figure 3). For such aircraft a cruise Mach No of 2.0. the requirements of performance and noise are conflicting. Engine Studies The various means of improving perfor- To provide the required engine data a mance and reducing noise were discussed in preliminary design study and part load per- some detail,in the Reference,and the con- formance estimate was made of four mixed straints to their application described. flow turbofan engines.These were two spool engines with the fan on the LP spool, In the next few sections the studies and the remainder of the core compression that have recently been made of engines for being carried by the HP spool,which was the next generation of supersonic trans- envisaged as an Olympus 593 HP spool with ports are described.These studies have some extra stages of compression. As is assumed a defined advancement in the level the case for the olympus 593,sufficient of technology available. nozzle area variation is provided to enable the appropriate LP spool rpm and TET ICAO Studies to be obtained simultaneously over a large range of flight conditions.This is an In November 1976 the ICAO Committee on essential feature of a supersonic cruise Aircraft Noise,CAN 5,set up Working engine. The ground rules for the study are Group E with the task of reporting to the given in Table 1,and some leading par- Committee (CAN 6)in late 1978 on recom- ticulars of the resulting engines are given mendations for SST noise regulations and in Table 2. guide lines.France,UK,US and USSR (as the countries who have a direct interest in SST development)have representation rights Cruise Design Point on the Working Group. Same core flow and overall pressure ratio as olympus 593 As part of their programme Working 16000K TET Group E set up a Parametric Study sub-group with the somewhat formidable task of evalu- Chosen bypass ratio ating the relationship between the noise Equal Mach Number and static pressure at mixing plane level and the operating cost of a supersonic (leads transport.Each country was to perform its to low operating point on fan chic) own studies,and report to the sub-group who would correlate the studies and report to Take-off Operation the Working Group,To assist in the cor- Cruise to take-off fan rpm relation simi- relation further sub-groups were set up, lar to olympus 593 LP compressor one on noise prediction,with the aim of 17000K TET achieving a common prediction method,and Highest safe operating point on fan chic another on economics having the task of Bypass ratio and overall pressure ratio agreeing a common method for cost follow estimation. NB Improved cruise performance is obtained Working Group E,when initiating the by allowing high operating point on fan Parametric Studies,made a forecast of the chic with unequal mixing Mach numbers timescale in which it expected the various technologies would be available for com- mencing a serious design.The technologies Table 1.-Mixed Turbofan Family m Engines were classified as: A,B,C.D.Ground Rules set at the Beginning of the Study Class I 1977-1980 Class II 1980-1985 Evident from Table 2 is the significant Class III Beyond 1985 reduction in bypass ratio from cruise to take-off which has resulted from the use The detailed classification of the various of variable bypass and optimising the cycle technologies is given by Foster in Table I matching during the course of the study. of Reference 2. In fact engine A is virtually a pure jet at 3

Advancements in Technoloqy In Reference 1 the authors have reviewed the application of advancements in tech￾nology to the performance improvement and noise reduction of supersonic transport requirements for subsonic aircraft have led to the adoption of low specific thrust, high bypass ratio engines, with a consequent reduction in jet velocities and hence in airport noise. It is also shown that this is not the case for supersonic cruise air￾craft where increasing bypass ratio beyond a certain value will degrade the mission performance (Figure 3). For such aircraft the requirements of performance and noise are conflicting. - aircraft. It is shown how performance The various means of improving perfor￾mance and reducing noise were discussed in some detail, in the Reference, and the con￾straints to their application described. In the next few sections the studies that have recently been made of engines for the next generation of supersonic trans￾ports are described. These studies have assumed a defined advancement in the level of technology available. ICAO Studies In November 1976 the ICAO Committee on Aircraft Noise, CAN 5, set up Working Group E with the task of reporting to the Committee (CAN 6) in late 1978 on recom- mendations for SST noise regulations and the countries who have a direct interest in SST development) have representation rights on the Working Group. Y guide lines. France, UK, US and USSR (as As part of their Droaramme Workina GrouD E set UD a Parametric Studv Sub-Orom .,I with' the SomEwhat formidable task of evalu￾ating the relationship between the noise level and the operating cost of a supersonic transport. Each country was to perform its own studies, and report to the sub-group who would correlate the studies and report to the Working Group. To assist in the cor￾relation further sub-groups were set up, one on noise prediction, with the aim of achieving a common prediction method, and another on economics havino the task of ~ agreeing a common method for cost estimation. Working Group E, when initiating the Parametric Studies. made a forecast of the The United Kingdom study is being under￾taken by British Aerospace (Filton and Weybridge) with engine data supplied by Rolls-Royce. In this study British Aerospace are evaluating operating costs and noise levels of a family of aircraft. The study covers variations in: Range Number of Passengers Wing Area Aspect Ratio Engine Bypass Ratio Class I1 technology is being assumed, with a cruise Mach No of 2.0. Enaine Studies To provide the required engine data a preliminary design study and part load per￾formance estimate was made of four mixed flow turbofan engines. These were two spool engines with the fan on the LP spool, and the remainder of the core compression being carried by the HP spool, which was envisaged as an Olympus 593 HP spool with some extra stages of compression. As is the case for the Olympus 593, sufficient nozzle area variation is provided to enable the appropriate LP spool rpm and TET to be obtained simultaneously over a large range of flight conditions. This is an essential feature of a supersonic cruise engine. The ground rules for the study are qiven in Table 1. and some leadina -. Dar￾ticulars of the Gesulting engines are given in Table 2. Cruise Design Point Same core flow and overall pressure ratio as Olympus 593 16000K TET Chosen bypass ratio Equal Mach Number and static pressure at mixing plane (leads to low operating point on fan chic) Take-off ODeration Cruise to take-off fan rpm relation simi￾lar to Olympus 593 LP compressor 17000K TET Highest safe operating point on fan chic Bypass ratio and overall pressure ratio follow E Improved cruise performance is obtained by allowing high operating point on fan chic with unequal mixing Mach numbers timescale in which'it expected the various technologies would be available for com- mencing a serious design. The technologies were classified as: A. B, C, D Ground Rules set at the Table 1 - Mixed Turbofan Family - Ensines Beqinninq of the Study Class I 1977-1980 Class I1 1980-1985 Evident from Table 2 is the significant Class 111 Beyond 1985 reduction in bvDass ratio from cruise to take-off which-kas resulted from the use The detailed classification of the various of variable bypass and optimising the cycle technologies is given by Foster in Table I matchinq durinq the course of the study. of Reference 2. In fact-engine-A is vihually a pure jet at 3

Engine A B C D Total airflow relative to datum 1.5 2.0 2.5 3.0 Design A,at beginning of study,= 0.5 1.0 1.5 2.0 Cruise Operating A,resulting from 0.291 0.762 1.240 1.716 optimum matching Cruise Thrust (1bf) 14500 14520 14410 14260 Cruise SFC relative to datum 0,990 0.972 0.967 0.970 Take-off operating入，resulting from 0.049 0.459 0.885 1,314 optimum matching Dry take-off thrust (1bf) 48280 50150 51370 53850 Dressed engine weight relative to datum 1.458 1.678 1.817 1,986 A=Bypass ratio A*=Design bypass ratio Quoted Cruise Mach 2.0,ISA 50C,53 000 ft Quoted Take-off 250 kt,ISA 100C,900 ft Quoted weight includes bypass duct,excludes mixer and primary nozzle Reheat for take-off if required Datum is Olympus 593 Mk 610 Table 2-Performance and Weight of Turbofan Family take-off.This variation of bypass ratio In order to provide British Aerospace is a natural feature of the layout described with a purejet tend point!for their where the fan and the remainder of the core studies,a further engine was considered. compression are on different spools and The leading particulars of this engine are nozzle variation is provided. It enables given in Table 3,and are based on a pro- the fan to be matched at high pressure ratio posal for a 15%flow increase over the for take-off.In contrast a turbojet,with- current engine.This is obtained by a mod- out the facility for allowing a sizeable ification to the first three stages of the quantity of LP compressor delivery air to current LP compressor.This modification bypass the HP system at cruise,needs to has been rig tested to show the required be matched at a low LP compressor pressure flow increase,and an earlier version has ratio at take-off to avoid LP compressor surge at cruise. Since the fan engines are matched at a Object: high fan pressure ratio at take-off rela- To provide BAe with "end point"for calcu- tive to a turbojet,the core has a rela- lations. tively higher degree of supercharge,and hence although the design core flow at Chosen Engine: cruise of the family of fan engines is the same as the olympus 593,the take-off core High temperature version of 1976 Olympus flow is some 30%to 40%higher.As a con- 593 Mk 622 proposal.Take-off airflow 15% sequence the dry take-off thrust is con- above Mk 610. siderably higher than would be given by an Olympus 593 turbojet operating at the same Leading Particulars: temperature.The necessity for reheat Cruise Mach 2.0 1SA+50C,53000ft boost at take-off is therefore minimised or TET 16000K eliminated,with consequent advantages in simplification of control equipment and Thrust 129801bf improved pollution characteristics. This SFC 1.034 x Datum also permits a shorter and hence lighter Take-ofE-250Kt,ISA+100℃，900ft exhaust system design.Eliminating reheat TET 17000K at take-off facilitates the use of ejector- type noise suppressors,as these would not Dry Thrust 377801bf easily withstand the peaky temperatures Reheated Thrust 49 300 1bf (18000K Reheat) involved in afterburner operation. Bare Engine Weight Plus Dressings 1.046 ×Datum(Datum is O1 ympus593Mk610） A more detailed discussion of the match- ing of the olympus 593 and various turbo- fan layouts has'been given by the authors 3. Table 3-Turbojet (=O)Engine

Enqine A B C D I Quoted weight includes bypass duct, excludes mixer and primary nozzle ~ 1.0 1.5 2.0 ~ ____ Design A , at beginning of study, = A * 0.5 Cruise Operating h , resulting from 0.291 0.762 1.240 1.716 optimum matching . Cruise Thrust. (lbf) 14 500 14 520 14 410 14 260 0.990 0.972 0.967 0.970 __ ~~ ... ~ . .. Cruise SFC relative to datum optimum matching Dry take-off thrust (lbf) 48 280 50 150 51 370 53 850 Dressed engine weight relative to datum 1.458 1.678 1.817 1.986 ~ _________ Take-off operating A , resulting from 0.049 0.459 0.885 i.314 - ~- .~ ~ Reheat for take-off if required Datum is Olympus 593 Mlc 610 Table 2 - Performance and Weight of Turbofan take-off. This variation of bypass ratio is a natural feature of the layout described where the fan and the remainder of the core compression are on different spools and nozzle variation is provided. It enables the fan to be matched at high pressure ratio for take-off. In contrast a turbojet, with￾out the facility for allowinq a sizeable quantity of LP compressor deiivery air to bypass the HP system at cruise, needs to be matched at a low LP compressor pressure ratio at take-off to avoid LP compressor surge at cruise. Since the fan engines are matched at a high fan pressure ratio at take-off rela￾tive to a turbojet, the core has a rela￾tively higher degree of supercharge, and hence although the design core flow at cruise of the family of fan engines is the same as the Olympus 593, the take-off core flow is some 30% to 40% higher. As a con- sequence the dry take-off thrust is con￾siderably higher than would be given by an Olympus 593 turbojet operating at the same temperature. The necessity for reheat boost at take-off is therefore minimised or eliminated, with consequent advantages in simplification of control equipment and improved pollution characteristics. This also permits a shorter and hence lighter exhaust system design. Eliminating reheat at take-off facilitates the use of ejector￾type noise suppressors, as these would not easily withstand the peaky temperatures involved in afterburner operation. A more detailed discussion of the match￾ing of the Olympus 593 and various turbo￾fan layouts has been given by the authors3 Family In order to provide British Aerospace with a purejet 'end point' for their studies, a further engine was considered. The leading particulars of this engine are given in Table 3,and are based on a pro￾posal for a 15% flow increase over the current engine. This is obtained by a mod￾ification to the first three stages of the current LP compressor. This modification has been rig tested to show the required flow increase, and an earlier version has w: To provide BAe with "end point" for calcu￾lations. 3hosen Enqine: Hiah temDerature version of 1976 01vmDuS 593 Mk 6'22 proposal. above Mk 610. Take-off airfiow 154 -eadincr Particulars: Cruise - Mach 2.0 ISA + 5OC, 53 000 ft TET 1600°K Thrust 12 980 lbf SFC 1.034 x Datum rake-off - 250 Kt, ISA + 10°C, 900 ft TET 170O0K Dry Thrust 37 780 lbf Reheated Thrust 49 300 lbf (18000K Reheat) aare Enqine Weioht Plus Dressinqs 1.046 x Datum (Datum is Olympus 593 Mk 610) Table 3 - Turbojet (A= 0) Encline 4